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Compressive strength test was carried out on the protein-based lightweight foamed concrete produced with cement partially replaced by rice husk ash to ascertain its strength characteristics. Standard concrete cubes of 150 x 150 x 150 mm were produced using ordinary Portland cement (OPC), fine aggregate, aqueous protein-based foaming agent and rice husk ash (RHA). The RHA was used to replace cement at 5 %, 10 %, 15 %, 20 %, 25 %, 30 %, 35%, 40 %, 45 % and 50 % by weight of cement. Control cubes with no cement replacement (0 %), were also produced and used as reference points for comparing the compressive strength of the lightweight foamed concrete at 28 days and 56 days respectively. The mix proportion of 1:1.5 was used as binder/fine aggregate proportions with the foam occupying 20 % of the volume of the concrete and the other constituents occupying the remaining 80 %. The compressive strengths of the lightweight foamed concrete at both 28 days and 56 days, increased for cement replacement levels of 5-30 % and gradually decreased for cement replacement levels of 35-50 % respectively for the mix proportion of 1:1.5 and for the water/binder ratio of 0.4. The minimum 28 days compressive strength for the mix proportion of 1:1.5 at cement replacement level of 30 % and water/binder ratio of 0.4 was 15.52 N/mm 2 while that at 56 days was 18.51 N/mm 2. The rice husk ash is a pozzolanic material with a capability of contributing up to 80 % and above to the compressive strength of lightweight foamed concrete, if the percentage replacement does not exceed 30 %. The mix proportion of 1:1.5 at water/binder ratio of 0.4 produces a structural lightweight concrete at 28 days.

This paper provides the results of structural reliability analysis carried out on the data of Nigerian grown Iroko tree (Chlorophora excelsa), to ascertain its structural performance as timber bridge beams. Five pieces of 50mm x 75mm x 3600mm of Nigerian grown Iroko hardwood were bought, seasoned naturally and 200 pieces of samples were prepared for determination of their strength properties, (which include bending strength parallel to grain, tensile strength parallel to grain, compressive strength parallel to grain, compressive strength perpendicular to grain and shear strength parallel to grain) at a moisture content of 18%, in accordance with the British Standard BS 373 of 1957. Statistical analysis was carried out using the strength properties for determination of mean, standard deviation, coefficient of variations, confidence limits and Chi-Square goodness of fits. Structural analysis and design of a timber bridge beam using the determined data from the Nigerian grown Iroko timber, in accordance with BS 5268 were carried out under the Ultimate Limit State of loading (ULSL). Reliability analysis was carried out to ascertain its level of safety using First-Order Reliability Method (FORM). Sensitivity analysis was also carried out by varying the depth of beam, imposed live load, breadth of the beam, unit weight of the Iroko timber, span of the beam as well as the end bearing length. The result revealed that the Nigerian grown Iroko timber is a satisfactory structural material for timber bridge beams at depth of 400mm, breadth of 150mm and span of 5000mm under the ULSL. The probabilities of failure of the Nigerian grown Iroko timber bridge beam in bending, shear, compression and deflection are respectively, under the specified conditions of loading.

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